1. Field of the Invention
The present invention relates to autothermal catalytic steam reforming of a hydrocarbon feedstock. In particular, the invention is directed to certain improvements of the known autothermal catalytic steam reforming processes, wherein an oxidant is supplied to a reacting process gas by means of a membrane.
2. Description of the Related Art
It is known in the art that a reactor with dense ceramic membranes that conduct oxygen can be used for syngas production (e.g. WO 98/48921).
Synthesis gas is produced in a membrane reactor by utilising the oxygen transported from the oxidant side of the membrane. Production of synthesis gas can be represented by the following three reactions:
CH4+H2O CO+3H2 
CH4+xc2xdO2CO+2H2 
CO+H2O CO2+H2 
In the above process inlet temperature of the gas will typically be between 500-800xc2x0 C. The pressure on the synthesis gas side of the membrane varies from ambient to 90 bar and the pressure on the air side from ambient to 26 bar.
The methane steam reforming and shift reactions are typically close to equilibrium at the reactor outlet.
By the invention the known membrane autothermal catalytic steam reforming process is improved by controlling the temperature gradient in the reactor, when employing a catalyst with reduced or no steam reforming activity in at least a top portion of the autothermal reactor.
Accordingly, this invention is a process for the preparation of a hydrogen and/or carbon monoxide rich gas from a hydrocarbon feedstock comprising partial oxidation of the feedstock with an oxidant supplied by permeation through a membrane and steam reforming of the feedstock in presence of a steam reforming catalyst being arranged on permeation side of the membrane, wherein steam reforming activity of catalyst is reduced in at least an inlet region of the catalyst bed.